Checking Email on Registration

[FatalBreeze]

When users are registered to my forum, i want to make sure they don't user certain email suppliers, in order to check this, i need to run some functions on the $vbulletin->GPC['email'] on registration. The problem is that the only hook there is "register_addmember_process" and it appears only after the email is validated and checked:

PHP Code:

$userdata->set('email', $vbulletin->GPC['email']); 


My question is, can i add a query on that hook like this:

PHP Code:

if(strstr($vbulletin->GPC['email'],...)) {
      $userdata->error('someerror');
} 


after the email is saved? or do i have to edit the file itself?
Thanks!